力学モデルを用いた椅子からの立ち上がり動作分析 : 足部位置ならびに体幹前傾角度の影響

健常男性10名を対象に、体幹の前傾角度及び足部位置の相違が椅子からの立ち上がり動作に及ぼす運動学的差異を検討した。体幹の前傾を増加させて立ち上がると、殿部離床時の身体重心?踵部距離と膝関節伸展モーメントが減少し、股関節伸展ならびに足関節底屈モーメントは増加した。足部を後方へ引いて立ち上がると、身体重心の前方移動距離と殿部離床時の身体重心?踵部距離が減少した。しかし、動作時の下肢関節ピークモーメント値に変化はなかった。以上の結果から、立ち上がりの際に足部を後方へ引いたり、体幹をより前傾させることによって、安定した姿勢で殿部を持ち上げることができるものと推察された。また体幹の前傾を増加させることで、股及び足関節の負担は増加するが、動作に必要な膝関節伸展筋群の負担を軽減できるものと考えられた。BACKGROUND : Standing from a seated position is a common activity of daily living, and essential for independent life. Many elderly and patients with musculoskeletal and neurological dysfunctions have difficulty in rising from a chair. Biomechanical analyses of chair rise are needed for the basis for more effective therapeutic programs. PURPOSE : The purpose of this study was to analyze the influence of initial foot position and trunk flexion on sit-to-stand (STS) transfer using a biomechanical model. METHODS : Ten healthy males performed the STS movement under 3 different conditions; 1) natural STS movement, 2) STS movement with increasing flexion of the trunk, 3) STS movement by placing the feet further back toward a chair. A motion analysis system and a force plate were used to collect kinematic and kinetic data. RESULTS : During the STS movement with the feet placed further back toward a chair, the distance between center of mass and base of support at seat off significantly decreased compared to that during the natural STS movement, but there were no siginificantly differences in lower limb moments. During the STS movement with increasing flexion of the trunk, the distance between center of mass and base of support at seat off, the moment of the knee significantly decreased, whereas moments of the hip and ankle significantly increased compared to those during the natural STS movement. CONCLUSIONS : The results suggest that placing the feet further back toward a chair or increased trunk forward lean is a more effective strategy to facilitate postural stability. Moreover, increased trunk forward lean is useful in reducing knee moment, although this strategy may be inefficient for the hip and ankle joints